Flotation recovery of molybdenum

ABSTRACT

A process for the separation and recovery of molybdenite from molybdenum concentrates which comprises treating the concentrate with a lignin sulfonate and subjecting the lignin sulfonateconcentrate mixture to froth flotation to separate copper sulfides, iron sulfides and insolubles present in the pulp concentrate and increase the molybdenum concentration.

United States Patent 1 Buza et al.

[ 51 Oct. 14, 1975 1 FLOTATION RECOVERY OF MOLYBDENUM [75] Inventors: Thomas Brian Buza; Martin Clifford Kuhn, both of Tucson, Ariz.

[73] Assignee: The Anaconda Company, New

York, NY.

22 Filed: Aug. 17, 1973 [21] Appl. No.2 389,146

Feed Alkali pH Conditioner Sultanate Conditioner l 2,070,076 2/ 1937 Brown 209/ 167 2,130,574 9/1938 Breerwood.... 209/167 2,187,930 1/1940 Brown 209/167 2,471,384 5/1949 Booth 209/167 2,664,199 12/1953 Barker 209/167 3,426,896 2/1969 Baarson 209/167 Primary ExaminerRobert Halper Attorney, Agent, or FirmPennie & Edmonds ABSTRACT A process for the separation and recovery of molybdenite from molybdenum concentrates which comprises treating the concentrate with a lignin sulfonate and subjecting the lignin sulfonate-concentrate mixture to froth flotation to separate copper sulfides, iron sultides and insolubles present in the pulp concentrate and increase the molybdenum concentration.

11 Claims, 2 Drawing Figures Rougher Insol Rougher Tails 1st Cleaner Tails 1st Insol Cleaner 2 nd Insol Cleaner 2nd Cleaner Tails 2nd Cleaner Concentrate Sheet 1 of 2 3,912,623

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FLOTATION RECOVERY OF MOLYBDENUM BACKGROUND OF THE INVENTION Molybdenite commonly occurs in copper-bearing ores. When such ores are beneficated by conventional froth flotation processes, using flotation reagents such as xanthates and dithiophosphates, the molybdenite floats with the copper sulfide and iron sulfide minerals. Since copper is the primary value in such ores, flotation plants are operated to produce optimum copper recovery without particular regard for the molybdenum obtained. Recovery of molybdenum value has, therefore, been obtained through processes of separating the molybdenum from copper cleaned molybdenum concentrates obtained by the flotation processes employing conventional flotation reagents.

Essentially, in these processes, the separation of molybdenite from the copper present in the concentrate is accomplished by either depressing the molybdenite with certain reagents while floating the copper or, conversely, by depressing the copper while floating the molybdenite. The processes presently known, however, involve the use of expensive reagents as well as extensive processing which often includes special treatment steps, such as roasting or steaming.

Several processes are well known in which the copper minerals are depressed and the molybdenite allowed to float and be separated by froth flotation techniques. These processes include the use of ferrocyanide-cyanide process in which the copper minerals are depressed with sodium ferrocyanide and subsequently depressed with sodium cyanide while the molybdenite is floated using fuel oil and alcohol frothers. Copper minerals may also be depressed with sodium hypochlorite and sodium ferrocyanide while allowing the molybdenite to be floated using fuel oil as a frothing agent. Caustic soda and phosphorous pentasulfide have also been used to depress the copper minerals of a sulfide ore and to separate the copper minerals from the molybdenite. These as well as other processes known to those skilled in the art involve the use of expensive reagents and processing steps which are both uneconomical and difficult to handle.

Processes in which the molybdenite is depressed from the copper minerals are also well known. Included in these are the use of a soluble dextrine which causes the depression of the molybdenite and allows for the copper minerals to be floated using such materials as ethyl xanthate as a collector. Other organic protective colloids, such as starch, glue, dextrose, gelatin, whey, casein, and the like as disclosed in US. Pat. No. 3,070,076 are also known to have the effect of inhibiting flotation of molybdenite and allow its separation from copper sulfides. These agents, however, also inhibit the flotation of such non-metallic materials as mica, talc, and the like, and, therefore, processes using them produce low concentrations of the molybdenite in the resultant tailings and are susceptible to breakdown under variations of concentration of the non-metallic materials.

Molybdenite has also been separated from copper sulfide and insolubles by spray-dryer techniques. This process is susceptible to breakdown due to the high concentrations of insoluble materials within the samples run.

SUMMARY OF THE INVENTION A process for the separation and recovery of molybdenite from molybdenite concentrate material has been discovered wherein the process in both economically feasible and which is not susceptible to breakdown due to high concentrations of insolubles within the sample.

The process comprises treating a molybdenite concentrate with a lignin sulfonate and subjecting the lignin sulfonate-pulp mixture to froth flotation to obtain a high concentration of molybdenite therefrom substantially free from insolubles. In a preferred embodiment, the pulp is conditioned with an alkali either prior to or together with addition of the lignin sulfonate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow diagram of an open-end flotation pro cess; and

FIG. 2 is a flow diagram of a locked-cycle flotation process.

DETAILED DESCRIPTION OF THE INVENTION A novel method has been obtained for floating insoluble type minerals and depressing molybdenite and thereby separating the latter from a molybdenite concentrate. The primary molybdenite-insoluble concentrate is treated with a lignin sulfonate to depress the molybdenite and allow the insoluble materials, such as the tremolites and talcs found therein, to float and to be separated therefrom. Good separation with high yields of molybdenite from copper sulfides, iron sulfides, and insoluble materials, irrespective of the concentration of these materials within the concentrate used, has been obtainable.

While copper is the prime value of the initial sulfide ores being processed, it is still realized that the recovery of molybdenum value as high-grade material is desirable from an economic standpoint. The art is, therefore, constantly seeking methods to improve the efficiency and/or lower the cost of molybdenum recovery from the ore without, at the same time, adversely affecting the copper recovery. The present invention is concerned with such a method.

Molybdenum sulfide commonly occurs in small concentrations in association with copper sulfide minerals. When the copper sulfide is concentrated by flotation techniques with such flotation reagents as alkaline xanthates, dithiophosphates or other known sulfhydryl collectors and the like, the molybdenum concentrate is collected in conjunction with insolubles, such as tremolites, silicates and talc-type minerals. This concentrate material is then subjected to a separate flotation circuit in which the concentrate is adjusted to an alkaline pH value and a lignin sulfonate added to allow successful flotation of the insoluble type materials along with copper sulfides and iron sulfides, used to thereby recover a high grade of molybdenum material. It has been found that, when a lignin sulfonate is used, the process is both economically advantageous and works efficiently with concentrate materials having a wide range of amounts of insolubles present.

The process is carried out by first adjusting the concentrate material to an alkaline pH. The alkalinity may be produced by the addition to the concentrate pulp of alkaline producing materials, such as soda ash, lime, or other alkali materials well known to those skilled in the art. The pH of the pulp concentrate may be any alkaline value, the preferred values being those above a pH of 10.

In adjusting the pH of the concentrate pulp to the desired value, it has been found that lime is the preferred alkali material for conditioning the pulp concentrate. Lime enhances the effect of the lignin sulfonate depressant used. The lime is added to the pulp concentrate in amounts ranging normally from about 20 to about 45 pounds per ton of concentrate, and the mixture is thoroughly agitated for short periods of time, such as about 5-10 minutes, to insure thorough distribution of the lime and to condition the concentrate. This pH adjustment or conditioning, as well as the subsequent steps, can be done on a continuous basis or by batch tech nique. When done in a continuous manner, the feed of the material and reagents used is added at such rates to allow for proper proportioning and the flow of the material is controlled to allow a residence time within any of the conditioning vessels to a time of at least that disclosed herein.

The alkali conditioned pulp material is then treated with a lignin sulfonate. The lignin sulfonates are ammonium and metallic sulfonate salts produced from the lignin of sulfite pulp-mill liquors. The molecular weight of the lignin sulfonate material normally ranges from about 1,000 to 20,000. Lignin sulfonates having a monomer unit molecular weight of about 840 have been found most useful in the process disclosed herein. The lignin sulfonate is used in amounts ranging from about 1 to about 7 pounds per ton of concentrate. It has been found that the use of lignin sulfonates as herein disclosed and claimed yields unexpectedly higher values of molybdenum values than other depressant agents heretofore known and used for recovery of molybdenite. The lignin sulfonate can also be added to the (molybdenum) pulp together with the alkali conditioning material, if desired, with good recovery also resulting.

In combination with the depressant agent, lignin sulfonate, the alkali pulp material may also be subjected at the same time to an agent which will further enhance the flotation of copper sulfides, iron sulfides, and the insoluble silicate materials. Any reagent known in the art, such as pine oil and an alkali xanthate and the like, may be used in association with the lignin sulfonate of this invention. The surface-active agent may be used in such quantities as from about 0.02 to about 0.2 pounds per ton of initial concentrate pulp material.

The lignin sulfonate and surface-active frother agents, which are added to the alkali conditioned pulp, are allowed to digest for from about 5 to 45 minutes with about 30 minutes being found satisfactory.

Subsequent froth flotation of the molybdenite concentrate may be effected in any of the well-known manners. The flotation separation of the molybdenite from the insoluble materials and copper sulfides may be accomplished by an open-ended process as depicted in FIG. 1 wherein the molybdenum concentrate feed and alkali material are first mixed together for a sufficient time to adjust the pH to alkalinity, then mixed with a lignin sulfonate to condition the material. The conditioned material is then subjected to a rougher flotation in which copper sulfides and insolubles are separated from the rougher tailings which contain a high concentration of the molybdenite values. The insolubles are subsequently treated to a number of flotation cleaners to separate further molybdenite values. The cleaner operations are refloats of the rougher concentrate. In the open-ended process, the rougher tailings and the tailings from each of the cleaner flotations contain the molybdenite material with the rougher tailings containing the dominant amount of molybdenite. It has been found that, in this process, combining the rougher tailings with the cleaner tailings of the first and second cleaners, yields an extremely high degree of the molybdenite values present in the original molybdenum concentrate.

Alternatively, the flotation separation may be carried out in a closed circuit as depicted in FIG. 2 in which the tailings of the first and second cleaners are recycled. In this system, the molybdenite values recovered are of extremely high degree, such as above percent, from the rougher tailing material.

The following examples herein disclosed are for illustrative purposes only and are not meant to be limiting upon the inventive concept except as set forth in the appended claims. All parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 A material obtained by flotation concentration and consisting mainly of molybdenite, copper sulfides, and insolubles was collected. The concentrate was conditioned for 5 minutes with 2 parts of lime per parts of feed to maintain a pH of 1 1.5. The pH measurements were made with a Beckman Zeromatic 11 pH meter using glass-calomal electrodes. To the conditioned material was then added 0.3 parts of a lignin sulfonate having molecular weight of 2,00015,000 with 2 to 4 monomer units per atom of sulfoxyl sulfur. American Cyanamid-Reagent 610). The material was allowed to digest for 30 minutes after which it was subjected to flotation in an Agitair flotation cell. The tailing was collected after 25 minutes and the concentrate subjected to two additional flotation cells for periods of 15 minutes each. The tailing material from each of the flotation cells was collected, vacuum filtered, and oven dried for assaying.

Table I shows the assay of the rougher flotation tailing, the first cleaner tailing, and the first cleaner concentrate. It is noted that a total of 93.9 percent of the molybdenum value is collected in the rougher tailing and first cleaner tailing.

TABLE I OPEN END FLOTATION RESULTS Assay Distribution Combined Rougher and 1st Cleaner Sample %Mo %Cu %Insol %Mo %Cu %lnsol %Mo Primary Mo Concentrate 27.6 1.24 42.90 Rougher Tail 46.2 .84 15.9 91.0 37.2 19.4 93.9 Calc. Rougher Conc. 5.36 1.65 77.6 9.0 62.8 80.6 lst Cleaner Conc. 4.06 1.72 80.4 6.1 58.7 75.0 1st Cleaner Tail 16.8 1.02 52.3 2.9 4.1 5.6

EXAMPLES 2-12 pH value of 11.5 in each sample. The samples had insoluble contents ranging from 14.8 to 42.9 and molyb- Various pulp concentrates of molbdenite, copper suldenum content ranging from 27.6 to 46.6 percent. The fides and insolubles were obtained in a manner similar rougher flotation cell and first cleaner flotation cell to that described in Example 1. The various samples 5 were treated in the same manner as described in Example l varying amounts of lime added so as to obtain the Distribution %Mo %Cu %Insol Assay %Cu %lnsol Sample Example Primary Mo Concentrate Rougher Tail Calculated Rougher Concentrate 1st Cleaner Concentrate 1st Cleaner Tail Combined Rougher and 4697 46 9 55 l 82 57 8 2 .0 4 .7 .68 T8 55 37 63 54 54 9 3 27 8 no 87 54 36 63 72 6 6 63 7 6 6 .2a a .2 1 5 5 3 6393 63 l8 8 90 9 5 27 365 54 27 63 36 M 2 2M 42 M 0009 2 8220 8 28 1 4 55 0 0 7 9 8 9 6 .59 3 2 392 9 H MUM-. H mm. 3% 7% WM H773 w 6%*8% ZSLL 0 4 .29 6 .39 .30 .59J 98884 8234.3 03260 84884798497 458 59928 i 7 4 774 37226 25 6264 25 36 7W7 49 50 58 7826 433 83 8 769263 7697 0 .6 995929195909 0719 3389 2 04000 1. 1.1 .1 .l 1.1 1 .1 .l .1 1 1. ALL L9136 l 3 1 8 7 7 7 .69 12 936220 421333 .5 .9 .4 .9 .9 24080 364083296 88 32 7 9 6 25 52 6 34 3 4 43 44 44 4 4 2 3 4 5 2 ll 4 m m m a a a r r -l t t t n n n m w m e n e B e e e n e C e a e m on d m M M 0 r m M m M I m M M H Cr m Re R 6 Re 6 U a Re e H a U ma m m m mflmm m m mm m C h w m CR CH h m C M ch ch .w 6 CM C m on]... mm mm 2 2. c 191...... mm mm. c wa m i u i i r mn m m m i m w mlc iemn rmw..c mom R oomoomoomo m mr u Rm oomo m m wun 0 Tm mm m CT CT CT wTmmm dw CT mTmmm nd mM .1 r .l [I Ir. r. cw em W ee weewefiwmflmm een wflflwmflm m 8 Bean 1 ee hh h .nh l elli hh l l e l iC am b a 3 p a a u CCb a a m CC ID 8 mm uk m mw w muw mw ummw m m mw um u m mm m noaamo fioofioofioo and m o flooflmo na o n PRC C PRRPRRD-RRPCRC 22C PRRD-CRC ZZSC P 3 4 5 6 7 8 9 0 1.

Calculated Rougher Concentrate Rougher Tail 1st Cleaner Concentrate 1st Cleaner Tail Combined Rougher and 1st Cleaner Primary Mo Concentrate Calculated Rougher Concentrate Rougher Tail Calculated 1st Cleaner Concentrate 1st Cleaner Tail 2nd Cleaner Concentrate 2nd Cleaner Tail Combined Rougher and 1st Cleaner 37 6 .A 3H 63 8 72 6 62 3 An 54 9 36 2 5 4 3m 7 24 9 3 9'1]. 12 2 7 9 36 63 265 46 03 40 11 ll 30 6 .2 209 42 4 4 3 m m m a I NC 6 HI n e e a h k n B C l @w em R ma 0 a r MdTdm e mrme we h c w a ufl um mkuk n aoa M PCRC 1 2 l EXAMPLES 13-15 A process was run in the same manner as described in Example 1 above on three molybdenum concentrate pulp samplings except that the tailings of the first cleaner flotation cell was recycled to the pH conditioner cell and the tailings of the second cleaner flotation cell was recycled to the first cleaner flotation cell. The pH of the initial feed plus first cleaner flotation cell additive was continuously adjusted with sufficient lime to maintain a pH of 1 1.5. Table 111 shows the assays of the various initial pulp concentrate and shows that a minimum of 96 percent of the molybdenum values was obtained from the initial rougher flotation tail material.

4. The process according to claim 1 wherein the initial froth flotation is allowed to be conducted for a period of at least 5 minutes.

5. The process of claim 1 wherein the alkali material and lignin sulfonate are contemporaneously added to the pulp material.

6. The process according to claim 1 including addition of a surface active agent which will enhance the flotation recovery in said float of copper, and other minerals that may be present in said pulp as iron sulfides, and insoluble silicate minerals.

7. A process for the separation and recovery of molybdenite values comprising conditioning a copper sul- TABLE III CLOSED CYCLE TEST RESULTS Assay Distribution Example Sample %Mo %Cu %lnsol %Mo %Cu %1nsol 13 Primary Mo Concentrate 41.3 .94 29.9

Rougher Tail 47.58 0.90 15.50 96.38 68.43 37.57 1st Cleaner Tail 26.9 0.69 41.0 Recirculate 2nd Cleaner Tail 15.6 0.70 49.0 Recirculate 2nd Cleaner Concentrate 5.34 1.25 76.89 3.62 v 31.56 62.42 14 Primary Mo Concentrate 39.6 .92 32.5

Rougher Tail 48.45 0.88 19.46 99.06 68.85 37.96 1st Cleaner Tail 20.0 0.81 50.2 Recirculate 2nd Cleaner Tail 10.2 0.70 63.5 Recirculate 2nd Cleaner Concentrate 1.15 0.99 79.17 0.94 31.15 62.04 15 Primary Mo Concentrate 42.8 1.27 22.9

Rougher Tail 47.82 1.08 7.85 97.82 69.15 32.20 1st Cleaner Tail 26.9 0.62 38.6 Recirculate 2nd Cleaner Tail 14.2 0.04 54.5 Recirculate 2nd Cleaner Concentrate 4.51 2.01 69.03 2.18 30.85 67.80

While the invention has been described in connection with a preferred embodiment, it is not intended to limit the invention to the particular form set forth but, on the contrary, it is intended to cover such alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

What is claimed is:

l. A process for separation and recovery of molybdenite values from a copper sulfide mineral concentrate containing molybdenite, comprising conditioning an aqueous pulp of said concentrate with sufficient alkali to render the pulp alkaline, treating the pulp with a sufflcient amount of a lignin sulfonate to depress the majority of molybdenite values and subjecting the thus treated lignin sulfonate-pulp mixture to froth flotation to produce a concentrate containing substantially all of the copper sulfide minerals and a tailing containing a high concentration of molybdenite.

2. The process according to claim 1 wherein the alkali material is calcium oxide and the pH value is at least 10.

3. The process according to claim 1 wherein the lignin sulfonate is selected from an alkali metal lignin sulfonate, alkaline earth metal lignin sulfonate, or ammonium lignin sulfonate.

fide mineral concentrate containing molybdenite with sufficient alkali to render the pulp alkaline, treating the conditioned pulp with a lignin sulfonate sufficient to depress the majority of molybdenite values, subjecting the lignin sulfonate-pulp mixture to an initial froth flotation from which the tail sampling is collected and the concentrate is further subjected to a second froth flotation from which the tail material is recycled and combined with the initial molybdenite pulp concentrate material and the second froth concentrate is subjected to a third froth flotation wherein the tailing is combined with the concentrate of the first froth flotation.

8. The process according to claim 7 wherein the alkali material is calcium oxide.

9. The process according to claim 7 wherein the lignin sulfonate is selected from the group consisting of an alkali metal lignin sulfonate, an alkaline earth metal lignin sulfonate or ammonium lignin sulfonate.

10. The process according to claim 7 wherein the pH is at least 10.

11. The process according to claim 9 including addition of a surface active agent which will enhance the flotation recovery of copper sulfides, and other minerals that may be present in said concentrate such as iron sulfides, and insoluble silicate minerals. 

1. A PROCESS FOR SEPARATION AND RECOVERY OF MOLYBDENITE VALUES FROM A COPPER SULFIDE MINERAL CONCENTRATE CONTAINING MOLYBDENITE, COMPRISING CONDITIONING AN AQUEOUS PULP OF SAID CONCENTRATE WITH SUFFICIENT ALKALI TO RENDER THE PULP ALKALINE, TREATING THE PULP WITH A SUFFICIENT AMOUNT OF A LIGNIN SULFONATE TO DEPRESS THE MAJORITY OF MOLYBDENITE VALUES AND SUBJECTING THE THUS TREATED LIGNIN SULFONATE-PULP MIXTURE TO FROTH FLOTATION TO PRODUCE A CONCENTRATE CONTAINING SUBSTANTIALLY ALL OF THE COPPER SULFIDE MINERALS AND A TAILING CONTAINING A HIGH CONCENTRATION OF MOLYBDENITE.
 2. The process according to claim 1 wherein the alkali material is calcium oxide and the pH value is at least
 10. 3. The process according to claim 1 wherein the lignin sulfonate is selected from an alkali metal lignin sulfonate, alkaline earth metal lignin sulfonate, or ammonium lignin sulfonate.
 4. The process according to claim 1 wherein the initial froth flotation is allowed to be conducted for a period of at least 5 minutes.
 5. The process of claim 1 wherein the alkali material and lignin sulfonate are contemporaneously added to the pulp material.
 6. The process according to claim 1 including addition of a surface active agent which will enhance the flotation recovery in said float of copper, and other minerals that may be present in said pulp as iron sulfides, and insoluble silicate minerals.
 7. A process for the separation and recovery of molybdenite values comprising conditioning a copper sulfide mineral concentrate containing molybdenite with sufficient alkali to render the pulp alkaline, treating the conditioned pulp with a lignin sulfonate sufficient to depress the majority of molybdenite values, subjecting the lignin sulfonate-pulp mixture to an initial froth flotation from which the tail sampling is collected and the concentrate is further subjected to a second froth flotation from which the tail material is recycled and combined with the initial molybdenite pulp concentrate material and the second froth concentrate is subjected to a third froth flotation wherein the tailing is combined with the concentrate of the first froth flotation.
 8. The process according to claim 7 wherein the Alkali material is calcium oxide.
 9. The process according to claim 7 wherein the lignin sulfonate is selected from the group consisting of an alkali metal lignin sulfonate, an alkaline earth metal lignin sulfonate or ammonium lignin sulfonate.
 10. The process according to claim 7 wherein the pH is at least
 10. 11. The process according to claim 9 including addition of a surface active agent which will enhance the flotation recovery of copper sulfides, and other minerals that may be present in said concentrate such as iron sulfides, and insoluble silicate minerals. 